The passage of the Clean Water Act in 1972 led to a boom in the construction of municipal wastewater treatment facilities needed to meet at least the minimum levels of treatment for the national drinking water supply.
A typical wastewater treatment plant comprises two treatment operations: a primary treatment, and a secondary treatment. The primary, or initial, treatment involves the removal of solids from an incoming waste stream. Larger objects are typically removed by “bar” screens, allowing smaller suspended and floating solids to pass. Downstream, scrum and grit may be removed before the remaining solids are permitted or forced to settle out in a primary settling tank. To accumulate and maximize the separation and settling of solids, a centrifuge-type action may be employed in connection with the settling tank. The accumulated solids, or “sludge,” are then carried away for treatment or disposal, while the remaining liquid is transported for secondary treatment involving aeration, activation, chemical treatment, etc.
The sludge that is removed from the wastewater is diverted from the settling tank in the primary treatment system to a conveyor or repository in the sludge treatment system for subsequent processing of the solids. The interconnection between the two systems (primary and sludge treatment) for transport of the sludge may be in the form of piping or ductwork. Due to the movement and vibration of rotating and other processing equipment (vibrators, air handlers, conveyors, etc.) in operating mechanical plant systems, some type of device is provided between certain interconnected components to dampen the vibration and inherent movement of mechanical components to protect the interconnected equipment and systems from damage. In a municipal wastewater treatment plant, the interconnection between sludge transport components is often in the form of a damper placed in-line between the inlet chute that is delivering sludge from a settling tank or basin, and the outlet chute that delivers the sludge to the conveyors or pumps that move the sludge to the sludge treatment system.
For many years, the damper that interconnects the inlet and outlet sludge chutes has been constructed of a heavy, reinforced solid, natural or butyl rubber. This rubber damper comprises an inlet flange, and outlet flange, and a flexible, sometimes bellows-like, body between the flanges. The body provides an open volume through which the sludge passes. While the heavy rubber construction is somewhat resistant to abrasion and harsh chemical exposure, it nonetheless requires routine maintenance, or replacement within the first several thousand hours of use. Even under the most favorable operational conditions, natural and butyl rubber damper constructions rapidly deteriorate, dry rot, and crack, requiring frequent repair (patching) or replacement that require the wastewater system to be removed from operation. The repair and/or replacement work unfortunately dictates loss of operational capacity with significant resulting costs.